Category Archives: Software

Downloading from Soundcloud

A couple years ago, downloading a song from Soundcloud used to be pretty trivial. Their server would send you the complete 128kbps MP3, and then the local embedded control would allow you to seek at will. Because the file arrived in one large chunk, it was both easy to identify in cache, and easy to copy somewhere else to play back. Sometimes this still works… You’ll know by looking at the dev console, and see if it shows a huge MP3 file transfer. If so, you’re in luck! Copy it from the cache and you’re set.

Evidently they’ve changed this practice for other tunes, possibly to improve the latency of seeking at random in tracks, or possibly because they don’t want people getting music they shouldn’t be able to get. You can get Greasemonkey scripts which put the download button back, but these simply fire the URL off to an third-party site which “somehow” reconstructs the song and then sends it back your way. Very black-box magic stuff indeed.

However – If you can stream it, you can download it, as they say. Let’s take a look at how Soundcloud actually gets a song to you, and see if we can still figure out how to download something we may not really be allowed to.

Start the browser’s Developer Console and then browse to a song you want to hear. Keep an eye on the “network” activity, it will give you clues as to what is actually going on. As the song begins playing, you’ll see a lot of small network requests to magically named files:

This seems promising. Download one or two and run “file” on it, and you get:
$ file *
c5f47vUnF3Ow.128.mp3?f10880d39085a94a0418a7e163b03d5226edfe2317e6aa1445547d76cf23a7ca5b08b0b9169eed2c0a13f681ab93c51d8e788dcaa887622ee2905d7463e4fd982e918b5b687caf75047026a3429731c5010a16: MPEG ADTS, layer III, v1, 128 kbps, 44.1 kHz, JntStereo
c5f47vUnF3Ow.128.mp3?f10880d39085a94a0418a7e167b03d5249919aaf544816306c9a5e3ca05a129454accfdda2750c51705ac2f68f036a37b2c482058312ab10625db87a6e3ab6dc1d1631dbd883a3f38786db484e66359daf667314eb8f03: MPEG ADTS, layer III, v1, 128 kbps, 44.1 kHz, JntStereo

Okay, so Soundcloud has broken the file into parts and is playing them back in sequence. You can pop one of these into your media player and listen to a portion of the song. We’re close, but how do we know where to find all these parts and put them together in order? Easy: there’s an m3u8 that has that for you – check the Dev Console again! Soundcloud’s player is using this to fetch the data in order from various URLs, and then stream it to you. For example, something like this:


An interesting aside, it seems these URLs time out after a short period of time, leading to 403 Forbidden errors if you try to access it again. No doubt these huge URL parameters point to some browser session or timestamp which becomes invalid after a while. If that happens, reload the page and start playing again to generate new files.

So to recap all this: we need to

  • take the m3u8 file,
  • retrieve each mp3 segment,
  • and concatenate them together.

Getting the m3u8 programmatically is hard, so just copy it from the browser : ) And to put these together you’ll need mp3cat installed – see for info.

#!/usr/bin/env perl
open(FP,"playlist.m3u8") or die "can't open playlist: $!";

my $piece = 0;
while( < FP > )
next if ($_ =~ m/^#/);
$filename = sprintf('outdir/%02s.mp3',$piece);
print `wget --no-check-certificate -O $filename $_`;

print `cat outdir/*.mp3 | mp3cat - - > output.mp3`;

Arduino Raytracer

Every programmer worth his salt has written a raytracer of some sort. It’s one of the classic “recursion exercises”, with a fair amount of math to wrap your head around. I’m not interested in writing one to run on the PC – there are already far more capable ones that can run on pretty much any hardware, complete with optimizations and features I couldn’t hope to implement in my lifetime.

Instead, I decided to write a raytracer which targets the Atmega 328 microcontroller in my Arduino! In the end, I succeeded in banging one together that calculates ray-triangle intersection, and each triangle can have a material attached with ambient / diffuse / transparent / reflective values and an RGB color. The scene is compiled in with a .h file (stored in PROGMEM), and outputs a PPM image pixel-by-pixel over the serial port.

The same engine can be used on the PC with a few modifications, so I was able to benchmark the performance of the Arduino in comparison with a modern laptop. The “detailed scene” rendered a 640×640 image in 263 seconds on the laptop. The same scene, scaled to only 64×64, still took 4008.471 seconds… in other words, the PC outperformed the Arduino by a factor of ~1500.

I posted the code, and further write-up, on the message board at this link: There are a lot of features that COULD be added here, but none that I actually intend to do. If I need a raytracer in the future, I’m just downloading POVRay : )

Crazy Taxi Garmin GPS Voice

Here is a project I’d been talking about for years, but never actually pulled it off until recently. It’s a voice set for a Garmin GPS, which replaces the default “narrator” with the obnoxious announcer from Crazy Taxi.
All voice clips were pulled from the PC version of the game, which had them in convenient .wav format already. Some trim / normalize with Audacity and import into Garmin Voice Studio to assemble together. I wanted to do more than just the announcer, but didn’t have any luck with that… there just weren’t enough clips to make it happen.

Here’s a video of the system in action:

I hosted all the downloadables on You can get it from here:


Before there was World of Warcraft, there was Everquest. I never played it but I had a buddy in college who did: he talked about how amazing the MMO genre was, with all its social aspects, technical quirks, and just plain cool experiences.

Naturally it inspired me to make my own clone. In Visual Basic. With 2d graphics and piping everything through the Winsock .ocx control. Full of programmer art made with a pirated copy of Bryce 3d.


Ah, the wide-eyed days of a young programmer in a rapidly expanding genre. It’s like I was playing out every cliche of the newbie at once. The one thing I had going for me, though, was a thorough understanding of the impossibility of such a project – and a sense of humor about it all. For example, I often joked that the only enemies were going to be Gelatinous Cubes, because that would be easy to render. I once wrapped a photo of my roommate’s face on a sphere to use for a hideous player character head. And so on. Eventually I got about as far as a character select screen, with a couple songs, before giving up and moving on to something else.

Unlike SlugFest, this is one that isn’t ever going to get off the ground. If anyone is interested in the art and music resources, you can have them: hereby released into the Public Domain.


This isn’t my only brush with the MMO genre. Later on some friends and I tried another take on it (“Draconis”) as the U of A Game Dev club project – with a result somewhat similar to The Mana World, and it once held up to five players online simultaneously. The real killer for these kind of games is the sheer amount of content required. Though Draconis worked technically, all the content in the world was viewable at first login. Hardly a compelling MMO experience.

Download GregerQuest Resources: .ZIP file, 1.9mb.

Smoke Help (for OSX)

This is a tool to help people quit smoking. My wife gave me the idea, I just wrote it.


Start the program up and put it into Learn Mode. Every time you have a cigarette, hit the “SMOKE” button. This trains the program, over the course of 100 cigarettes, your (natural) average time between cigarettes.

Then put it into Coach Mode. At this point the program will begin telling you when it’s time to smoke again, using an alarm. Don’t smoke until instructed to do so, and then hit the button when you do. The program starts by alarming at the learned rate, but extends the interval each cigarette. Eventually your rate will slow down to the point where quitting is natural.

At least, in theory. My wife quit without my help so I wasn’t ever able to test it.

This is the sort of thing that would be super-ideal as a mobile app. I don’t have time nor inclination to set that up, but I’d love to see it. So, this is now public domain software. (Included font isn’t though).

Smoke Help OSX Binary – .zip – 2.45 MB
Smoke Help source code – .tar.gz – 227kb

Minus Infection

I took a programming languages class in college, which used Scheme to demonstrate concepts like lexers, parsers, etc. The final project was to write our own interpreted object-oriented language. I enjoyed the class but never quite got the hang of Scheme. So when the time came to write the language, I did the minimum possible in Scheme, and implemented the rest as a standard library add-on to my own language.

Cutting things to the bare minimum resulted in a language with only seven constructs, and the only arithmetic operation was subtraction. Addition would thus be implemented as minus (a, minus(0, b)). IF statements were simply WHILE loops that ran zero or one times. And so on.

Sadly, I don’t have the source code any more. But I do have the README file.

Minus Infection
A Programming Language by
Greg Kennedy

I. Introduction
What is Minus Infection? MI is a programming language which aims to be Turing complete and support object-oriented programming with as few primitives as possible. It is written in Scheme. Functionality is provided by external Library files, which define many of the functions you would otherwise miss from your favorite language.
Because of this, the actual implementation of MI is rather simple, but powerful enough that you can use the built-in functions to build vastly more complicated ones.

But why? Scheme is a fine language. It is really quite powerful. But I just can’t get the hang of all those parentheses and cars and cdrs. So I thought I’d minimize the work I had to do in Scheme, and instead move that work into MI. It’s also sort of an experiment for me to discover just how little is really needed to make a usable language.

II. How do I use it?
MI source files are simply text files – create them in Notepad or vi or whatever.
Your source file is the main routine of your program.

III. What are the primitives?
MI recognizes as “true” any expression which evaluates to less than 0, and “false” as any expression which evaluates to “equal to or greater than 0” (i.e. “not false).

The only variable type MI understands is integer arrays. You can create single variables in your source and omit the subscript when later referencing them – the parser will simply fill in the missing subscript with a [0].

See section 4 for methods for dealing with strings. Internally they are represented (like in C) as an array of integers representing character codes.

Arrays maintain their own sizes and will warn of an out-of-bounds access. For strings, no special termination character is needed.

These primitives are built-in to MI:
MINUS (X, Y) – perform the calculation X – Y and return the result.
LTZ (X) – returns -1 if X is less than 0, 0 otherwise.
WHILE (COND, BLOCK) – continually executes BLOCK as long as COND is true.
SET (X, EXP) – sets X to the evaluated result of expression EXP.
INT (NAME, SIZE) – declares an array named NAME of length SIZE
DOT (NAME, MEMBER) – OO operator: call member function or access member variable
PRINT (x) – Prints X to the screen. X is a string.

IV. What is in the libraries?
You’ve no doubt noticed that the language seems a little sparse. That’s because all the real functionality comes from the libraries.
To load a library, simply place this command in your source file:
LIB “FILENAME” – when parsing, this line causes the execution of FILENAME.

The standard library is called default.lib. It provides the following functions:
< (X, Y), > (X, Y), = (X, Y),
<= (X,Y), >= (X, Y) – Conditionals returning true if X (op) Y.
IF (COND, BLOCK1, BLOCK2) – if COND is TRUE, executes BLOCK1; else executes BLOCK2
– (X, Y) – behaves like MINUS
+ (X, Y) – calculates X + Y, returns result
*, /, % (X,Y) – multiply, divide, modulus
AND(X,Y), OR(X,Y), XOR(X,Y) – boolean operations.
FOR(X, COND, INC, BLOCK) – Similar to C for loops
STRCPY (X, Y) – copies string Y over string X.

V. Example code?
This program prints “Hello, World!” to the screen.

LIB "default.lib"
STRCPY(HWORLD,"Hello, World!");
PRINT(HWORLD); Bringing a Nuke to the Loudness War

Ever heard of the Loudness War? It’s the steady ramp-up in perceived volume that has plagued popular music for the past 30+ years. Producers have steadily chipped away at dynamic range in an effort to make a hotter track. Audio signal-to-noise ratio suffers. Nowadays the typical radio song has a 3-6 dB dynamic range (for comparison, CDs have a theoretical 96 dB range).

Well folks: I’m playing to WIN. Here is a compressor that scales ALL of your peaks to 100%: in other words, compression at a ratio of INFINITY : 1… or a dynamic range of 0. TAKE THAT, PRODUCERS.

Here’s an example in action, cutting from Clair de Lune. First, the original. Then, the RADIO-READY version.

Doesn’t this just sound so much more… hip / edgy / loud / etc?

Interestingly, I tried it on a selection of pop music. It makes for a great demonstration of “listener fatigue”. – zip file containing Perl script, 1.7 kB

cfg_parse – Simple Config File Parser in C

There is no standard way in C to parse config files. Several libraries have sprung up to solve the problem, but perhaps that is overkill for what should be a simple operation.

Presenting: cfg_parse – a compile-in solution for reading key-value pairs from file(s), looking up settings, and writing a config file back to disk. I could write more about it, but the included main.c shows all the functionality.

// driver test program for cfg_parse

#include "cfg_parse.h"


int main(int argc, char **argv)
// Pointer to a cfg_struct structure
struct cfg_struct *cfg;

// Initialize config struct
cfg = cfg_init();

// Specifying some defaults

// "Required" file
if (cfg_load(cfg,"config.ini") < 0)
fprintf(stderr,"Unable to load cfg.ini\n");
return -1;

// Several "optional" files can be added as well
//  Each subsequent call upserts values already in
//  the cfg structure.

// Retrieve the value for key INFINITY, and print
printf("INFINITY = %s\n",cfg_get(cfg,"INFINITY"));

// Retrieve the value for key "KEY", and print
printf("KEY = %s\n",cfg_get(cfg,"KEY"));

// Delete the key-value pair for "DELETE_ME"

// Dump cfg-struct to disk.

// All done, clean up.

return 0;

Download: cfg_parse.1.0.tar (version 1.0, 4kb .tar.gz)

iNES Header Fixer

Auditing ROM collections has been made much simpler over the years thanks to concerted efforts of many cartridge purchasers, dumpers, cataloguers, and coders.  Using a combination of RomCenter (or ClrMamePro) and a No-Intro .Dat file, one can quickly fix an entire collection in one go: repairing names, verifying regions, checking for problem ROMs, producing have-lists, etc etc.

NES roms throw a particular curveball because they carry a 16-byte header with a little info about the board within the cart.  Emulators need this info, but it isn’t verified by No-Intro since it’s not part of any real dump.  As a result iNES headers remain missing, incorrect, or filled with crap data.  A new repair tool is needed. is a Python script which can repair defunct iNES headers using an external cart database.  It does this by extracting the data portion from the file, calculating a crc32, looking for the crc the xml file, and then rebuilding a header based on that info.  If the old and new headers differ, the file is overwritten with a fixed version.

Be careful with this tool: it’s sort of a blunt object, and may trash your rom collection if not used carefully.  Make backups.  In particular it writes only iNES v1 headers, expecting emulators to cope with the shortcomings of this format.

Output samples:
-> No change to existing header

CRC check: 4318A2F8
Found CRC match: Barker Bill's Trick Shooting
*** Header unchanged: not writing replacement file.

-> Adding a battery

CRC check: 1F6EA423
Found CRC match: Baseball Simulator 1.000
oldHeader: 4e45531a081010000000000000000000
newHeader: 4e45531a081012000000000000000000
All done.  Wrote new file roms/Baseball Simulator 1.000 (USA).nes

-> Correcting a mapper, vertical mirroring, and removing “DiskDude!”

CRC check: 9BDE3267
Found CRC match: Adventures of Dino Riki
oldHeader: 4e45531a0204004469736b4475646521
newHeader: 4e45531a020431000000000000000000
All done.  Wrote new file roms/Adventures of Dino Riki (USA).nes

-> Standardizing on “horizontal mirroring”

CRC check: 3ECA3DDA
Found CRC match: Bases Loaded 3, Ryne Sandberg Plays
oldHeader: 4e45531a101041000000000000000000
newHeader: 4e45531a101040000000000000000000
All done.  Wrote new file roms/Bases Loaded 3 (USA).nes

-> Adding a missing header

CRC check: 50CCC8ED
Found CRC match: Battleship
newHeader: 4e45531a020430000000000000000000
All done.  Wrote new file roms/Battleship (USA).nes

Here’s the script:

Converts NES ROMs to iNES format, applying correct iNES header.
Usage: ines-fix 
Supported infile formats are .nes, .pas (headerless .nes)

ROM data is recognized by CRC32 using BootGod's master XML database
  so make sure you have a local copy

import sys
import struct
from binascii import crc32
from xml.etree import ElementTree

##### String holding location of cart db
cart_xml = "NesCarts (2011-09-10).xml"
# uncomment next line to use Nestopia's DB instead
# cart_xml = "NstDatabase.xml"

# Other required vars
i_fmt = 'p'
blob = None
found = 0
oldHeader = ""

# Parse command-line

if (len(sys.argv) != 2):
    print "Usage: " + sys.argv[0] + " "

# Open rom database
#print "Attempting to open cart db " + cart_xml
tree = ElementTree.parse(cart_xml)
#print "DB opened!"

# Attempt to open supplied rom file

    with open(sys.argv[1], "rb") as f:
        tag =
        if (tag == "NES\x1A"):
            i_fmt = 'i'
            oldHeader =

#        print "Detected " + i_fmt + " format for input file"

        blob =

except IOError as (errno, strerror):
    print "Error opening " + sys.argv[1] + ": "
    print "I/O error({0}): {1}".format(errno, strerror)

if (len(blob) > 0):
    format_crc32 = format(crc32(blob) & 0xFFFFFFFF, '08X')
    print "CRC check: " + format_crc32

    # go look up crc32 in db
    game_list = tree.findall("game")
    for game in game_list:
        cart_list = game.findall("cartridge")
        for cart in cart_list:
            if (cart.attrib.get('crc') == format_crc32):
        if (found):

    if (found == 0):
        print sys.argv[1]
        print "*** CART NOT FOUND IN DB"
        print "----------------------------------------------------"

print "Found CRC match: " + game.attrib.get("name").encode('ascii', 'ignore')

# retrieve data from game
board = cart.find("board")
mapper = int(board.attrib.get("mapper"))

prg_size = 0
prg_list = board.findall("prg")
for prg in prg_list:
    prg_size = prg_size + int(prg.attrib.get("size") [:-1])

chr_size = 0
chr_list = board.findall("chr")
for chr in chr_list:
    chr_size = chr_size + int(chr.attrib.get("size") [:-1])

battery = 0
wram_list = board.findall("wram")
for wram in wram_list:
    if (wram.attrib.get("battery") is not None):
        battery = int(wram.attrib.get("battery"))

chip_list = board.findall("chip")
for chip in chip_list:
    if (chip.attrib.get("battery") is not None):
        battery = int(chip.attrib.get("battery"))

mirror_4 = 0
mirror_v = 0
pad = board.find("pad")
if (format_crc32 == "CD50A092" or \
    format_crc32 == "EC968C51" or \
    format_crc32 == "404B2E8B"):
    mirror_4 = 1
elif (pad is not None):
# the "h" pad means "v" mirror
    mirror_v = int(pad.attrib.get("h"))

mapper_lo = mapper & 0x0F
mapper_hi = mapper & 0xF0

newHeader = "NES\x1a" + \
              struct.pack("BBBB", \
                ( prg_size / 16 ), \
                ( chr_size / 8 ), \
                (mapper_lo << 4) + (mirror_4 << 3) + (battery << 1) + (mirror_v)
, \
                (mapper_hi) ) + ( '\0' * 8 )

if (newHeader != oldHeader):
    print "*** HEADER UPDATED ***\noldHeader: " + oldHeader.encode('hex')
    print "newHeader: " + newHeader.encode('hex')

    # write new file
        with open(sys.argv[1], "wb") as f:
            f.write( newHeader )
            f.write( blob )

    except IOError as (errno, strerror):
        print "Error opening " + sys.argv[1]
        print "I/O error({0}): {1}".format(errno, strerror)

    print "All done.  Wrote new file " + sys.argv[1]
    print "*** Header unchanged: not writing replacement file."
print "----------------------------------------------------"

For those having problems with copy-paste, you can download a .zip containing the script here:

Timewave v1.2

Timewave is a 2-d space shooter written in C++ using some of the freely available SDL libraries. It runs on Windows, Linux, and Mac OSX (10.4 or later). The object of this game is to fight through the mass of enemies in each level, defeat the level boss, and finally destroy the (well-armed) enemy space station far from Earth.

It has an interesting “twist” in which you can alter the flow of time. Build up your time meter by playing the game in fast-forward. Playing in slow motion affords you some extra maneuvering room but depletes the meter. If you achieve a high score, you can choose a color flag to represent your ship and have yourself recorded on the high score table.

This game is ‘freeware’ – you can download it and copy it around to anyone you like, you can even alter the graphics to better suit your tastes if you wish, but don’t pull my name off it and try to pass it off as your own work. You can’t get the source code though because it’s a total wreck. I may go and try cleaning it up later for a release, but until then, the binaries in the download should work just fine.

Last updated Aug. 7, 2007 – click for full-size

Recent Changelog

  • Reduction in resource file sizes: some items converted to 256-color, optipng and audio editing shaved further bytes.
  • Renamed hiscore.dat to config.ini, and added more options.
  • New command line options: -f (switch to Fullscreen mode), -c (Create Config: just write config.ini and exit), -w (switch to Windowed mode)
  • Added a “Change Keys” button which allows users to alter the inputs.
  • Added “Arcade Mode” switch to the config.ini file. This causes the game to simulate an arcade machine on Free Play: the title screen rotates with the high score table.
  • The arrow keys now drive the cursor on the high score color picker table.
  • Mac OSX port (PPC / Intel Universal Binary, 10.4 or greater).

Last updated May 3, 2012